Axial-flux modular permanent-magnet generator with a toroidal winding for wind-turbine applications

Permanent-magnet (PM) generators have been used for wind turbines for many years. Many small wind-turbine manufacturers use direct-drive PM generators. For wind turbine-generators, the design philosophy must cover the following characteristics: low cost, light weight, low speed, high torque and variable-speed generation. The generator is easy to manufacture and the design can be scaled up for a larger size without major retooling. A modular PM generator with axial flux direction was chosen. The permanent magnet used is NdFeB or ferrite magnet with flux guide to focus flux density in the air gap. Each unit module of the generator may consist of one, two, or more phases. Each generator can be expanded to two or more unit modules. Each unit module is built from simple modular poles. The stator winding is formed like a torus. Thus, the assembly process is simplified and the winding insertion in the slot is less tedious. The authors built a prototype of one unit module and performed preliminary tests in their laboratory. Follow-up tests will be conducted in their laboratory to improve the design.